The amount of “hedging” language—words that suggest room for doubt—used by prominent newspapers in articles about climate change has increased over time, according to a new study by the University of Colorado Boulder.

The study, published in the journal Environmental Communication, also found that newspapers in the U.S. use more hedging language in climate stories than their counterparts in Spain.

“We were surprised to find newspapers increased their use of hedging language, since the scientific consensus that climate change is happening and that humans are contributing to it has substantially strengthened over time,” said Adriana Bailey, a doctoral student at CU-Boulder’s Cooperative Institute for Research in Environmental Sciences, or CIRES, and lead author of the paper.

CIRES is a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration.

The researchers examined articles published in two U.S. papers, The New York Times and The Wall Street Journal, and in two Spanish papers, El Mundo and El Pais. The articles used for the study were published in 2001 and 2007, years when the Intergovernmental Panel on Climate Change, or IPCC, released its latest assessments of the physical science basis for climate change.

The researchers combed the articles for words from all parts of speech that typically suggest uncertainty, such as almost, speculative, could, believe, consider, blurry, possible and projecting.

Once the words were identified, the scientists considered the context they were used in to determine if they should count as hedging language.

For example, the word “uncertainty” was counted in a New York Times article that read “…substantial uncertainty still clouds projections of important impacts…” but it was not counted in a sentence in the same newspaper that read “...uncertainty was removed as to whether humans had anything to do with climate change…”

Also, the researchers only counted hedging language that had to do with either the physical science basis for climate change—such as changes in average temperatures and precipitation patterns—or the IPCC process. Language related to possible adaptation and mitigation efforts, such as preparing coastal cities for expected sea level rise, was not included.

The results showed that in 2001, the U.S. papers used 189 hedging words or expressions per 10,000 words printed while the Spanish papers used 107. In 2007, the number of hedging words and expressions used per 10,000 words rose to 267 in the U.S. and to 136 in Spain.

Given that Spain has ratified the Kyoto Protocol—the international agreement to limit greenhouse gas emissions—while the U.S. has not and that Spain has proposed a national climate policy, the research team was not surprised to find that Spanish newspapers seem to be communicating less uncertainty about climate change than U.S. papers.

But the team did not expect to see increases in hedging language in both countries over time. The study was not designed to determine the reasons for the increase, but Bailey said it could be related to a number of factors, from amplified politicization of climate change—including polarization of climate stances by political leaders—to the possibility that reporters are actually writing more about the detailed science, which requires greater explanation of the accompanying scientific uncertainties.

The researchers also noticed that the ways in which qualifications are introduced into climate change articles have evolved over time.

“One of the new ways uncertainty is being constructed is by comparing IPCC reports and climate studies against each other, and in that way, presenting results that seem disparate,” said Bailey, who also is affiliated with CU-Boulder's Department of Atmospheric and Oceanic Sciences. “The second new way is by comparing predictions to observations—by describing climate changes that are happening faster than expected or that are smaller than anticipated, for example.

“Making sense of these ‘surprises’ is part of the scientific process; it’s how we build new knowledge,” she added “But news stories don’t often provide readers with the background information necessary to understand this.”

While this study analyzed news articles that appeared after the IPCC’s third and fourth assessment reports, the researchers say the findings can help people better interpret media coverage of more recently released reports on climate change, including the IPCC’s fifth assessment, which was published last year.

An awareness of how the media use hedging language to cover the changing climate can help media consumers distinguish remaining scientific questions from uncertainties constructed by the news, the researchers said.

Other CU-Boulder co-authors of the study are Maxwell Boykoff, an assistant professor at CIRES, and Lorine Giangola, STEM coordinator for the Graduate Teacher Program.

Quotes

“We were surprised to find newspapers increased their use of hedging language, since the scientific consensus that climate change is happening and that humans are contributing to it has substantially strengthened over time,” said Adriana Bailey, a doctoral student at CU-Boulder’s Cooperative Institute for Research in Environmental Sciences, or CIRES, and lead author of the paper.